1. Field of the Invention
The present invention relates generally to spring assisted return mechanisms. More particularly, the present invention relates to a steering wheel return assist apparatus having a spiral spring and which permits a limited degree of free rotation of the steering wheel before the activation of the return assist device.
2. Disclosure Information
A known steering gear used in many vehicles today is a rack and pinion type steering gear wherein a pinion gear connected to the steering shaft of a steering column assembly meshingly engages a plurality of gear teeth exposed upon a rack member. Rotating the steering wheel causes the pinion gear to rotate in the gear teeth of the rack member, causing reciprocal movement of the rack member to thereby steer the road wheels of the vehicle. After a turn has been made, the torque produced by the steering wheels in conjunction with the tie rods and the rack member often cause the pinion gear to travel to its basic neutral position. However, due to the weight of the vehicle and other such factors such as friction between the rack and pinion as well as in the steering column itself, the steering wheel often does not return to a near central neutral position without some effort by the driver of the vehicle. This can be annoying to the driver of the vehicle particularly during slight turns or while driving at highway speeds. Therefore, there is a need for a steering wheel return assist mechanism to return the steering wheel to the near central neutral position after a turn to facilitate ease in handling of the vehicle. In this respect, it would be advantageous to allow the steering shaft to freely rotate a limited amount before the return assist apparatus was activated to prevent over-steering of the vehicle due to the added assist from the mechanism especially while maintaining straight ahead driving.
Various spring assisted return devices have been proposed which utilize a spring to bias a shaft to a near central neutral position after the shaft has been rotated. For example, U.S. Pat. No. 2,714,000 discloses a mechanism for returning a deflected instrumentality to a central zero position. This mechanism discloses the use of a dual spring mechanism wherein each of the springs are directly in contact with the rotating shaft of the measuring device. The device however, does not allow for limited degree of free rotation of the shaft before actuation of the spring mechanism.
U.S. Pat. No. 3,636,794, assigned to the Assignee of the present application, and Norwegian Patent No. 101,790 also disclose spiral springs employed as return assist mechanisms. The '794 patent discloses the use of a single spiral spring as a steering return assist mechanism but does not teach or suggest the use of such spring in a device wherein a limited degree of free rotation of the shaft is permitted. The Norwegian Patent discloses the use of a pair of spiral springs in a arrangement for connecting a drive arrangement depending upon the changing workloads. The springs also do not allow a limited degree of free rotation of the driving shaft.
It is a feature of the present invention to provide a steering wheel return assist mechanism which permits a limited degree of free rotation of the steering shaft before engagement of the spiral spring of the apparatus.
It is an object of the present invention to provide a steering wheel return assist mechanism which includes a first and second return assist devices to return the steering wheel to a near central neutral position after the steering wheel has been turned in either direction.
These and other objects and features of the present invention will be apparent from the drawings, description and claims which follow.